Such a cartridged blank ammunition is described in the U.S. Pat. No. 5,936,189. This cartridge ammunition is used in connection with automatic firearms of medium caliber of approx. 40 mm. A plurality of such cartridges are accommodated in a belt, which is then fed to an automatic firearm.
The propellant chamber in the cartridge shell is subdivided into a high-pressure chamber in which the propellant charge is accommodated and a low-pressure chamber which is in communication with the high-pressure chamber via overflow openings. Cartridge shell and projectile are mechanically connected via a central screw connection which is designed as a rated break point.
If the propellant charge in the high-pressure chamber is pyrotechnically ignited by means of a primer, the propellant charge burns off, develops propellant gases with a high pressure which, then, act on the projectile bottom in both chambers and finally expel the projectile from the cartridge shell, after the rated break point between cartridge shell and projectile had been broken at a specific pressure.
A similar cartridge ammunition is described in the U.S. Pat. No. 4,892,038.
Moreover, blank cartridges of this type are known, in which only a low-pressure propellant chamber is provided; such cartridges are designated as low-velocity cartridges.
A great number of pieces of such a cartridge ammunition are used and must both be safely stored and safety transported from the manufacturer to a user. As a rule, storage and transport are carried out in larger containers, e.g. sheet-metal boxes which accommodate a plurality of such cartridges.
Despite the not insignificant amount of igniting agent for primers and propellant charge, which is located in a storage or transport container, storage and transport are customarily unproblematical. At most, a fire in the storage or transport room represents a risk, during which temperature of around 220° C. and more are reached.
However, at such temperatures the pyrotechnical igniting charge of the primer is already ignited, which, then, also ignites the actual propellant charge, which, otherwise, is only ignited at from 320° C. to 400° C. After the igniting of the propellant charge such a pressure is built up as in a customary shot in the propellant chamber which acts on the projectile bottom so that, finally, after the breaking up of the mechanical connection between cartridge shell and projectile they are explosively flung apart.
A considerable damage can be caused alone due to the amount of the exploding propellant charges of a plurality of cartridges. However, the cartridge shells and projectiles which are explosively flung apart may also cause a lot of damage. Here, both cartridge shell and projectile virtually act as projectiles. Any accommodation containers are destroyed due to this, the cartridge shells and projectiles which are driven apart may also endanger persons and cause a lot of mechanical damage.
During tests such cartridges were placed into a heating dish, whereupon the heating dish was slowly heated. After the ignition temperature of the primer of about 220° C. had been reached, the primer was first of all ignited—as described—and by means of the same subsequently the propellant charge of the cartridges. Due to the building up of pressure in the propellant chamber cartridge shell and projectile are driven apart and flung up to a distance of 100 meters so that the energy which is released by many such cartridges during a fire is quite conceivable.
In order to avoid a tearing apart of cartridge shell and projectile and a damage to the environment in the case of a high increase in the outside temperature above the ignition temperature and/or self-ignition temperature of the pyrotechnical ignition charge, e.g. in the case of a fire, it is known both from DE 102004017465 and the corresponding WO 2005/098348, to provide at least one and preferably several passage(s) starting from the propellant chamber which penetrate the wall of the cartridge shell and are filled with a solid, pressure-tight, meltable material whose melting point is lower than the lowest ignition temperature of one of the pyrotechnical charges of the cartridge, i.e. lower than the ignition temperatures of the pyrotechnical ignition charge and the propellant charge.
Such a melting material is e.g. a melting metal. Such melting metals are e.g. alloys of bismuth and tin, other metals such as lead, etc. being possibly still added.
If, accordingly, a cartridge of the type in question is heated up to the melting temperature of the melting material and/or melting metal of e.g. 140° to 180° C., the melting material melts in the passages between the propellant chamber in the cartridge shell and the outside environment. If with the temperature still increasing the primer and, finally, even the propellant charge are ignited by this, no pressure can build up in the propellant chamber, since the exposed passages act as pressure relief openings. Due to this, the propellant charge only burns off, it being possible that the propellant gases generated due to this may escape through the relief openings. Cartridge shell and projectile are not separated from each other in this fashion so that neither a damage due to pressure nor a mechanical damage is caused.
This was confirmed in tests, in which a plurality of such cartridges were accommodated in a customary transport box made of sheet metal. Not even the sheet metal box was substantially damaged.
The passage or the passages irrespective of its (their) design (is) are designed in such a way that in the case of a normal shooting of the projectile from the cartridge shell the melting material withstands the high pressures within the propellant chamber.